INCOMING!: метеорита в Челябинске, Russian Meteor - February 2013 Options

[ugordan]

Considering that the worked-out orbital parameters are bound to be highly uncertain, I'd say looking for it in past imagery would be a futile effort. It came in from the sunward direction, that means it was only visible in night skies a good while ago and the positional uncertainty calculated for that epoch would be huge, I guess.

[Holder of the Tw...]

I agree. The odds of it having been spotted in the past are very small anyway. Asteroids the size of this meteor have an absolute magnitude in the range of 26 to 28, depending on how bright the material. For the best modern surveys like Pan-STARRS, the rock has to be within 0.1 AU of earth if it is abs mag 26, and within 0.05 AU if it is 28, in order be picked up. Even then you have to get lucky, with it favorably placed with a low phase angle.

Only a small fraction of earth crossers this size have been spotted. Even fewer with enough observations to get a rough orbit plotted. Then most of those are lost and never seen again. A check of the MPC database shows that about 890 near earth asteroids have had their orbits plotted that are as dim or dimmer than this meteor was likely to be. Six of those so far have been spotted on a subsequent pass (or opposition) near the earth. None of them have been located on archived data from a previous pass that was prior to their discovery.

For comparison, so far they've found about 25% of the asteroids that would currently be classified as "potentially hazardous", which have to have absolute magnitudes at least as bright as 22, a hundred times brighter than mag 27.

Looks like a small meteoroid decided to spoil 2012 DA14's big day ...

True, but the meteor may have immortalized 2012 DA14, at least as a side note. Possible future quote:

" ... on that day, astronomers were focused on another small asteroid, 2012 DA14, which by an incredible coincidence happened to be in the neighborhood at the same time..."

[Mongo]

A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid

In February 15 2013 a medium-sized meteoroid impacted the atmosphere in the region of Chelyabinsk, Russia. After its entrance to the atmosphere and after travel by several hundred kilometers the body exploded in a powerful event responsible for physical damages and injured people spread over a region enclosing several large cities. We present in this letter the results of a preliminary reconstruction of the orbit of the Chelyabinsk meteoroid. Using evidence gathered by one camera at the Revolution Square in the city of Chelyabinsk and other videos recorded by witnesses in the close city of Korkino, we calculate the trajectory of the body in the atmosphere and use it to reconstruct the orbit in space of the meteoroid previous to the violent encounter with our planet. In order to account for the uncertainties implicit in the determination of the trajectory of the body in the atmosphere, we use Monte Carlo methods to calculate the most probable orbital parameters. We use this result to classify the meteoroid among the near Earth asteroid families finding that the parent body belonged to the Apollo asteroids. Although semimajor axis and inclination of the preliminary orbit computed by us are uncertain, the rest of orbital elements are well constrained in this preliminary reconstruction.

[centsworth_II]

http://m.youtube.com/#/watch?v=t5DgXLbjaQQ

Video linked from orbit reconstruction study in previous post.

[Greenish]

A substantial writeup at http://neo.jpl.nasa.gov/news/fireball_130301.html
Don Yeomans & Paul Chodas, Additional Details on the Large Fireball Event over Russia on Feb. 15, 2013 NASA/JPL Near-Earth Object Program Office March 1, 2013

....The fireball was observed not only by video cameras and low frequency infrasound detectors, but also by U.S. Government sensors. As a result, the details of the impact have become clearer....
New Fireball DataU.S. Government sensor data on fireballs are now reported on the NASA Near-Earth Object Program Office website at
http://neo.jpl.nasa.gov/fireballs

[Bill Harris]

Thanks-- that confirms a lot of the speculation that we were tossing around last month.

--Bill

[Mongo]

The orbit of the Chelyabinsk event impactor as reconstructed from amateur and public footage

A ballistic reconstruction of a meteoroid orbit can be made if enough information is available about its trajectory inside the atmosphere. A few methods have been devised in the past and used in several cases to trace back the origin of small impactors. On February 15, 2013, a medium-sized meteoroid hit the atmosphere in the Chelyabinsk region of Russia, causing damage in several large cities. The incident, the largest registered since the Tunguska event, was witnessed by many thousands and recorded by hundreds of amateur and public video recording systems. The amount and quality of the information gathered by those systems is sufficient to attempt a reconstruction of the trajectory of the impactor body in the atmosphere, and from this the orbit of the body with respect to the Sun. Using amateur and public footage taken in four different places close to the event, we have determined precisely the properties of the entrance trajectory and the orbit of the Chelyabinsk event impactor. We found that the object entered the atmosphere at a velocity ranging from 16.0 to 17.4 km/s in a grazing trajectory, almost directly from the east, with an azimuth of velocity vector of 285$^o$, and with an elevation of 15.8$^o$ with respect to the local horizon. The orbit that best fits the observations has, at a 95% confidence level, a semi-major axis a = 1.26$\pm$0.05 AU, eccentricity e = 0.44$\pm$0.03, argument of perihelion $\omega$=95.5$^o\pm2^o$ and longitude of ascending node $\Omega$= 326.5$^o\pm0.3^o$. Using these properties the object can be classified as belonging to the Apollo family of asteroids. The absolute magnitude of the meteoroid was H= 25.8, well below the threshold for its detection and identification as a Potential Hazardous Asteroid (PHA). This result would imply that present efforts intended to detect and characterize PHAs are incomplete.

There are several lessons we can learn from this work. (1) To confirm the fundamental role that active enthusiasts, a.k.a. citizen astronomers, can play in scientific research, especially in cases when unexpected events occur. (2) We are missing half of the PHAs by our own definition of what a PHA is. (3) Although objects smaller than 100 m cannot produce global damage they can still produce significant local damage. (4) A simple calculation shows that if the impactor had been delayed by about 3.5-4 minutes, the impact would have taken place over central Europe, where the damage could have been much greater. (5) The object approached Earth from the Sun side, which is not covered by current optical surveys. This side is totally unshielded.

[ElkGroveDan]

This side is totally unshielded.

As are all the other sides. Perhaps the authors meant, "This side is totally unmonitored."

[dvandorn]

I find it interesting that in the histories of the development of the Saturn V rocket, a big deal is always made of the fact that if the rocket were to ever explode on the launch pad, it would result in a blast the size of a "fair-sized nuclear weapon." However, the yield estimate for an exploding Saturn V was given as between 3 and 5 kilotons.

So, to put it into perspective, this meteor exploded in a blast roughly 100 times more powerful than an exploding Saturn V rocket...

-the other Doug

[ugordan]

So, to put it into perspective, this meteor exploded in a blast roughly 100 times more powerful than an exploding Saturn V rocket...

Yes, but it exploded about 10 times farther away from any observers than an on-pad Saturn V explosion would have. Shockwave overpressure IIRC roughly drops off as the inverse cube of distance so they're kind of in the same ballpark, especially if you consider that the 5 kT estimate for Saturn V is pretty generous.

[Mongo]

The Earth Impact Effects Program requires a diameter of 26.5m and density of 3100 kg/m^3 to be input in order to produce the stated numbers (entry velocity 16.7 km/s, trajectory 15.8 degrees from horizontal, airburst energy 440 kt, shock wave travel time 1.48 minutes). This yields a mass of 30 thousand tonnes for the object.

Of course the results are only as accurate as the underlying physics model of the simulation.

[mchan]

As are all the other sides. Perhaps the authors meant, "This side is totally unmonitored."

Perhas the authors meant, "This side is totally unshielded from the sun."

[silylene]

I find it interesting that in the histories of the development of the Saturn V rocket, a big deal is always made of the fact that if the rocket were to ever explode on the launch pad, it would result in a blast the size of a "fair-sized nuclear weapon." However, the yield estimate for an exploding Saturn V was given as between 3 and 5 kilotons.

So, to put it into perspective, this meteor exploded in a blast roughly 100 times more powerful than an exploding Saturn V rocket...

-the other Doug

That brought to mind the Feb. 15 1996 low altitude explosion of the Long March rocket over China (which is a lot less explosive power than a Saturn 5). Video in this link, the blast damage to the occupied buildings and homes on the ground was horific. Long March explosion.